In U.S. Pat. No. 3,067,315, issued Dec. 4, 1962 to Bohdan Hurko, there is disclosed a heating unit comprising a glass-like base member with a narrow continuous strip of multi-layer film bonded to such member, such film comprising at least one inner layer of platinum and an outer layer of gold so that the total resistance of the narrow strip is approximately equal to the low resistance of the outer gold layer. In putting heating units such as covered by the patent to Hurko on so-called life tests, it was found that the multi-layer films cracked, peeled or agglomerated at early points in such tests thereby giving an intolerable increase in the electrical resistivity of the films. Accordingly, the heating units such as herein disclosed were developed.
It is, therefore, an object of the present invention to provide new and novel electric heating units which are relatively durable.
It is another object of the present invention to provide electric heating units whose heating elements are substantially protected against cracking, peeling or agglomeration thereof.
Other objects and characteristic features of the invention will become apparent as the description proceeds.